text: The concentration of the gel determines the pore size of the gel which affects the migration of DNA.  The resolution of the DNA changes with the percentage concentration of the gel. Increasing the agarose concentration of a gel reduces the migration speed and improves separation of smaller DNA molecules, while lowering gel concentration permits large DNA molecules to be separated. For a standard agarose gel electrophoresis, 0.7% gel concentration gives good separation or resolution of large 5–10kb DNA fragments, while 2% gel concentration gives good resolution for small 0.2–1kb fragments.  Up to 3% gel concentration can be used for separating very tiny fragments but a vertical polyacrylamide gel would be more appropriate for resolving small fragments.  High concentrations gel, however, requires longer run times (sometimes days) and high percentage gels are often brittle and may not set evenly. High percentage agarose gels should be run with PFGE or FIGE.  Low percentage gels (0.1−0.2%) are fragile and may break. 1% gels are common for many applications.